They are probably talking about mining for nickel, which in Canada at least is an open-pit process.

The nickel is going to be mined for other industrial uses anyway, so it really isn't a valid argument. Similar arguments are used with tantalum and its use in cell phones, but it's just not logical. There are a myriad of other uses for the metal, it is going to be mined regardless.

The difference in nickel use in battery production is that the process (foaming nickel metal for use in battery cells) is fairly nasty environmentally, while other uses for nickel (steel alloys, for instance) aren't as environmentally questionable.